1. Field of the Invention
This invention relates in general to a disk drives, and more particularly to disk drives having tracks spaced apart according to the width of the written track.
2. Description of Related Art
Variations in track pitch due to the orientation of the head through the arcing motion of the support arm are well known. FIG. 1 illustrates a head 110 flying over a plurality of tracks 112, 114 on a recording medium 120. In FIG. 1, the recording head 110 is generally centered over a first track 112. The track pitch 130 is the distance between the centerline 132 of the first track 112 and the centerline 134 of the second track 114. Variations in the track pitch 130 due to the orientation of the head 110 through the arcing motion of the support arm are well known. In fact, in a conventional disk drive with a sector servo system the track pitch typically varies from inner-diameter (ID) to outer-diameter (OD). This is because using a rotary actuator causes a different skew angle of the recording head from ID to OD. Common skew angles may vary several degrees from the ID to the OD. Because of this skew angle the track pitch at ID is typically about 4% higher than the track pitch at the OD.
However, each recording surface in all conventional disk drives with a sector servo system and two or more recording surfaces have the same track pitch at a given radius. Since the skew angle of the head varies from ID to OD, the track pitch may be selected to be less at the outer-diameters. Still, the track pitch is the same at the same radius on different disk surfaces.
The dimensional tolerance of the written track depends mostly on the dimensional tolerance of the width of the writing element of the recording head. Minor effects on the width of the written track include the medium coercivity and magnetic spacing. The dimensional tolerance of the writing element width depends mostly on the photolithographic processes used to make the recording head. Over the past few years, the size of magnetic heads have continued to decrease. While the size of magnetic heads continue to decrease, the tolerance for processing magnetic heads is not decreasing as fast as the desired nominal width of the head. As a consequence, the ratio of the tolerance to the nominal value of the write head is increasing with each new disk drive product having higher areal density. As a result, heads having significant variation in width are produced. To accommodate the track pitch spacing design, heads must be sorted to select those which will allow the desired track pitch. Further, due to the relatively poor tolerance of the photolithographic processes used to make the recording head, heads that do not meet the given track pitch have to be discarded.
It can be seen that there is a need for a method and apparatus for providing a track pitch on a recording surface that is determined by the width of the tracks written by the head for the recording surface.
It can be seen that there is a need for a method and apparatus for providing a disk drive having a track pitch that varies form recording surfaces due to the width of the write element so that heads need not be sorted to achieve a fixed track pitch relationship between each recording media in a disk drive.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a disk drive having tracks spaced apart according to the width of the written track.
The present invention solves the above-described problems by providing a method and apparatus for providing a track pitch on a recording surface that is determined by the width of the tracks written by the head for the recording surface therefore eliminating the need to discard unmatched heads as required when a fixed relationship of the track pitch between different storage media in a storage device is desired.
A method in accordance with the principles of the present invention includes the steps of calculating the width of a write element to be associated with a storage medium and determining the track pitch for the storage medium based upon the calculated width of the write element.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the step of calculating the width of the write element further comprises the steps of writing a pattern on a storage medium at a predetermined radius using the write element associated with the storage medium to form a written track, moving the head across the written track to read an amplitude sensed from the written track by the head element, and ascertaining the width of the write element based upon the sensed amplitude.
Another aspect of the present invention is that the step of ascertaining the width of the write element comprises the steps of determining the amplitude of the sensed signal, identifying a one-half amplitude point on a rising edge of the sensed signal and a one-half amplitude point at a falling edge of the sensed signal and computing the distance between the two points.
Another aspect of the present invention is that the pattern written on the storage medium further comprises a constant frequency pattern.
Yet another aspect of the present invention is that the step of determining the track pitch for the storage medium further comprises the step of adjusting the determined track pitch for the storage medium based upon the width of the write element to account for different skew angles of the head as the head is positioned from inner-diameters to outer-diameters.
Another aspect of the present invention is that the skew angle increases as the head is positioned from the inner-diameters to the outer-diameters allowing the track pitch to decrease from the inner-diameters to the outer-diameters.
Another aspect of the present invention is that the skew angle decreases as the head is positioned from the inner-diameters to the outer-diameters allowing the track pitch to decrease from the outer-diameters to the inner-diameters.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.